Utilization of starch and clay for the preparation of superabsorbent composite

Starch and attapulgite were utilized as raw material for synthesizing starch-graft-poly(acrylic acid)/attapulgite superabsorbent composite by graft copolymerization reaction of starch and acrylic acid (AA) in the presence of attapulgite micropowder in aqueous solution. Major factors affecting on water absorbency such as weight ratio of AA to starch, initial monomer concentration, neutralization degree of AA, amount of crosslinker, initiator and attapulgite were investigated. The superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10 wt% exhibit absorption of 1077 g H(2)O/g sample and 61 g H(2)O/g sample in distilled water and in 0.9 wt% NaCl solution, respectively. This superabsorbent composite with excellent water absorbency and water retention under load, being biodegradable in nature, economical and environment-friendly, could be especially useful in agricultural and horticultural applications.     

Synthesis,characterization and swelling behaviors of sodium alginate-g-poly(acrylic acid)/sodium humate superabsorbent

A novel sodium alginate-g-poly(acrylic acid)/sodium humate superabsorbent was prepared by graft copolymerization with sodium alginate, acrylic acid and sodium humate in aqueous solution, using N,N’-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The effects of crosslinker, sodium alginate and sodium humate content on water absorbency of the superabsorbent were studied. The swelling behavior in solutions of various pH and the swelling kinetics in saline solutions (5 mmol/L NaCl and CaCl₂) were also investigated. The results from IR analysis showed that both sodium alginate and sodium humate react with the acrylic acid monomer during the polymerization process. The introduction of sodium humate into the sodium alginate-g-poly(acrylic acid) system could enhance the water absorbency and the superabsorbent containing 10 wt% sodium humate acquired the highest water absorbency (1380 g/g in distilled water and 83 g/g in 0.9 wt% NaCl solution).     

Synthesis and characterization of a novel super-absorbent based on wheat straw

In order to develop an eco-friendly polymer, a novel super-absorbent polymer was prepared by graft copolymerization of acrylic acid (AA), acrylic amide (AM) and dimethyl diallyl ammonium chloride (DMDAAC) onto the pretreatment wheat straw (PTWS). The molecular structure of the super-absorbent was confirmed by FTIR. The factors that can influence absorbencies of the super-absorbent resin (SAR) were investigated, such as weight ratio between the monomers, the ratio of PTWS to monomers, the amount of initiator and cross-linker, temperature reaction time and neutralization degree of AA. The SAR has the water absorbency of 133.76 g/g in distilled water and 33.83 g/g in 0.9 wt.% NaCl solution.     

Crosslinked carboxymethylchitosan-g-poly(acrylic acid) copolymer as a novel superabsorbent polymer

A novel carboxymethylchitosan-g-poly(acrylic acid) (CMCTS-g-PAA) superabsorbent polymer was prepared through graft polymerization of acrylic acid onto the chain of carboxymethylchitosan and subsequent crosslinking. It was demonstrated by FTIR spectroscopy that acrylic acid had been graft polymerized with carboxymethylchitosan. The thermal stability of the polymer was characterized by thermogravimetric analysis. By studying the swelling ratio of the polymer synthesized under different conditions, optimization conditions were found for a polymer with the highest swelling ratio. The rate of water absorption of the polymer was high, and the swelling of the polymer fitted the process of first dynamics. The swelling ratio of the polymer was pH-dependent.     

Synthesis and characterization of a novel cellulose-g-poly(acrylic acid-co-acrylamide) superabsorbent composite based on flax yarn waste

A new, low-cost, and eco-friendly cellulose-based superabsorbent was successfully prepared from flax yarn waste. The method used was a free-radical graft copolymerization of AA and AM onto a cellulose backbone in a homogeneous aqueous solution. APS was used as the initiator in the presence of a crosslinker, MBA. The effects of various factors on water absorbency were discussed. The factors included reaction temperature, initiator amount, monomer amount, salt solution type, and solution pH. Under the optimized conditions, the water absorbencies of the obtained superabsorbent composite were 875 g/g distilled water, 490 g/g natural rainwater, and 90 g/g 0.9 wt% aqueous NaCl solution. The product also had excellent water retention and salt resistance properties. Fourier-transform infrared spectroscopy and scanning electron microscopy were employed to examine the structure of the prepared superabsorbent.     

Sugarcane bagasse derivative-based superabsorbent containing phosphate rock with water-fertilizer integration

To improve the water-fertilizer utilization ratio and mitigate the environmental contamination, an eco-friendly superabsorbent polymer (SPA), modified sugarcane bagasse/poly (acrylic acid) embedding phosphate rock (MSB/PAA/PHR), was prepared. Ammonia, phosphate rock (PHR) and KOH were admixed in the presence of acrylic acid to provide nitrogen (N), phosphorus (P) and potassium (K) nutrients, respectively. Impacts on water absorption capacity of the superabsorbent polymer (SAP) were investigated. The maximum swelling capacity in distilled water and 0.9wt.% (weight percent) NaCl solution reached 414gg(-1) and 55gg(-1) (water/prepared SAP), respectively. The available NPK contents of the combination system were 15.13mgg(-1), 6.93mgg(-1) and 52.05mgg(-1), respectively. Moreover, the release behaviors of NPK in the MSB/PAA/PHR were also studied. The results showed that the MSB/PAA/PHR has outstanding sustained-release plant nutrients property.     

Synthesis of superabsorbent from carbohydrate waste

A mixture of acrylamide (AM) and acrylic acid (AA) monomers were grafted on germinated gelatinized wheat starch using potassium persulfate (KPS) as an initiator to yield superabsorbent. The effects of different parameters such as time, temperature, monomer feed (AM:AA), starch: monomers ratio and initiator concentration on graft add-on were studied, and the optimized values were found to be 2 h, 60 °C, 1:1 (w/w), 1:1(w/w) & 1% (with respect to starch powder), respectively. The product so formed was saponified with 0.1N NaOH, dried and finely powdered sample was characterized using FT-IR, TGA. Product showed maximum absorbency of 150 g/g.     

Preparation and properties of a double-coated slow-release NPK compound fertilizer with superabsorbent and water-retention

A double-coated slow-release NPK compound fertilizer with superabsorbent and water-retention was prepared by crosslinked poly(acrylic acid)/diatomite - containing urea (the outer coating), chitosan (the inner coating), and water-soluble granular fertilizer NPK (the core). The effects of the amount of crosslinker, initiator, degree of neutralization of acrylic acid, initial monomer and diatomite concentration on water absorbency were investigated and optimized. The water absorbency of the product was 75 times its own weight if it was allowed to swell in tap water at room temperature for 2 h. Atomic absorption spectrophotometer and element analysis results showed that the product contained 8.47% potassium (shown by K(2)O), 8.51% phosphorus (shown by P(2)O(5)), and 15.77% nitrogen. We also investigated the water-retention property of the product and the slow release behavior of N, P and K in the product. This product with excellent slow release and water-retention capacity, being nontoxic in soil and environment-friendly, could be especially useful in agricultural and horticultural applications.     

Synthesis and characterization of a novel super-absorbent based on chemically modified pulverized wheat straw and acrylic acid

In order to develop an eco-friendly polymer, the material was prepared from pulverized wheat straw by chemical methods. And a super-absorbent hydrogel has been synthesized with chemically modified pulverized wheat straw (CMPWS) and acrylic acid (AA) in aqueous solution. Factors, such as weight ratio of AA to CMPWS, the amount of initiator and cross-linker, temperature and neutralization degree of AA that influence absorbencies of super-absorbent were investigated. Moreover, the super-absorbent had been proved with expectant polymerization structure and good thermo-stability via IR spectrum and TGA analysis. The morphological features were evidenced by SEM images. The excellent product was obtained with the absorbencies of 417 g/g in distilled water and 45 g/g in 0.9 wt% NaCl solution.     

Chitosan membranes modified by contact with poly(acrylic acid)

In this work chitosan membranes modified by contact with poly(acrylic acid) (PAA) aqueous solution at two different temperatures (25 °C and 60 °C) were obtained. The pure chitosan (CS) membranes, as well as those treated with PAA (CSPAA_25 and CSPAA_60) were characterized by FTIR-ATR, water sorption capacity, thermal analysis (TG/DTG), and scanning electron microscopy (SEM). In addition, in vitro permeation experiments were carried out using metronidazol and sodium sulfamerazine aqueous solutions at 0.1% and 0.2% as model drugs. FTIR-ATR results showed the presence of absorption bands of and COO⁻ indicating the formation of a polyelectrolyte complex between chitosan and poly(acrylic acid). The results also indicated that PAA penetrates deeper into the membrane at higher temperature (60 °C), forming a thicker complex layer. Polyelectrolyte complex formation as well as the influence of treatment temperature was confirmed by lower hydrophilicity, higher thermal stability, and lower permeability of the treated membranes. The results show that the methodology used is a simple and very efficient way to drastically change some membrane properties, especially their permeability.     

Biodegradable superabsorbent hydrogels derived from cellulose by esterification crosslinking with 1,2,3,4-butanetetracarboxylic dianhydride

Superabsorbent hydrogels were prepared from native celluloses dissolved in lithium chloride and N-methyl-2-pyrrolidinone (LiCl/NMP) by esterification crosslinking with 1,2,3,4-butanetetracarboxylic dianhydride (BTCA). Subsequent conversion of the unreacted carboxyl groups to sodium carboxylates by the addition of aqueous NaOH was performed to enhance the water affinity of the gels. The absorbency of the products was strongly dependent on the amount of BTCA that was esterified to cellulose, and the highest absorbency was observed for the hydrogel composed of approximately 0.25 molecules of BTCA per anhydroglucose unit (AGU) of cellulose. Furthermore, it was confirmed that the absorbency was enhanced as the average degree of polymerization (DP) of the starting cellulose increased. The use of cotton cellulose with a high DP of about 2400 produced a hydrogel with an absorbency of 720 times its dry weight, which exceeded the absorbency of commercial crosslinked sodium polyacrylate superabsorbent hydrogel (SPA). The hydrogels exhibited good biodegradability, with a maximum degradation of 95% within 7 days using cellulase.     

Preparation, characterization and properties of superabsorbent nanocomposites based on natural guar gum and modified rectorite

Novel guar gum-g-poly(sodium acrylate)/rectorite (GG-g-PNaA/REC) superabsorbent nanocomposites were prepared in aqueous solution using guar gum (GG), partially neutralized acrylic acid (NaA), acidified rectorite (H⁺-REC) and organified rectorite (CTA⁺-REC) by cetyltrimethylammonium bromide (CTAB) as raw materials, ammonium persulfate (APS) as initiator and N,N′-methylenebisacrylamide (MBA) as crosslinker. FTIR spectra confirmed that NaA had been grafted onto GG chains and the OH groups of REC participated in polymerization reaction. Exfoliated nanocomposite was obtained for H⁺-REC and intercalated structure was formed for CTA⁺-REC as shown by XRD results. SEM observations show REC has been uniformly dispersed in polymeric matrix. Effects of HCl concentration, organification degree of CTA⁺-REC and content of REC on swelling capabilities were investigated and the swelling kinetics of nanocomposites was evaluated. Results indicate that modifying REC by acidification and organification can improve swelling properties of the resultant nanocomposites, and GG-g-PNaA/CTA⁺-REC exhibited higher swelling capability and swelling rate contrast to GG-g-PNaA/H⁺-REC.     

Direct patterning of poly(acrylic acid) on polymer surfaces by ion beam lithography for the controlled adhesion of mammalian cells

Poly(acrylic acid) (PAA)-patterned polystyrene (PS) substrates were prepared by ion beam lithography to control cell behaviors of mouse fibroblasts and human embryonic kidney cells. Thin PAA films spin-coated on non-biological PS substrates were selectively irradiated with energetic proton ions through a pattern mask. The irradiated substrates were developed with deionized water to generate negative-type PAA patterns. The surface characteristics of the resulting PAA-patterned PS surface, such as surface morphology, chemical structure and composition and wettability, were investigated. Well-defined 100 μm PAA patterns were effectively formed on relatively hydrophobic PS substrates by ion beam lithography at higher fluences than 5 × 10¹⁴ ions/cm². Moreover, based on the in vitro cell culture test, cells were adhered and proliferated favorably onto hydrophilic PAA regions separated by hydrophobic PS regions on the PAA-patterned PS substrates, and thereby leading to the formation of well-defined cell patterns.     

Synthesis and self-assembly of well-defined poly(amino acid) end-capped poly(ethylene glycol) and poly(2-methyl-2-oxazoline)

Poly(ethylene glycol) (PEG) and poly(2-methyl-2-oxazoline) (PMOx) are water-soluble, biocompatible polymers with stealth hemolytic activities. Poly(amino acid) (PAA) end-capped PEG and PMOx were prepared using amino-terminated derivatives of PEG and PMOx as macroinitiators for the ring-opening polymerization of γ-benzyl protected l-glutamate N-carboxyanhydride and S-benzyloxycarbonyl protected l-cysteine N-carboxyanhydride, respectively, in the presence of urea, at room temperature. The molecular weight of the PAA moiety was kept between M(n) = 2200 and 3000 g mol(-1). PMOx was polymerized by cationic ring-opening polymerization resulting in molecular weights of M(n) = 5000 and 10,000 g mol(-1), and PEG was a commercial product with M(n) = 5000 g mol(-1). Here, we investigate the self-assembly of the resulting amphiphilic block copolymers in water and the effect of the chemical structure of the block copolymers on the solution properties of self-assembled nanostructures. The PEG-block-poly(amino acid), PEG-b-PAA, and PMOx-block-poly(amino acid), PMOx-b-PAA, block copolymers have a narrow and monomodal molecular weight distribution (PDI < 1.3). Their self-assembly in water was studied by dynamic light scattering and fluorescence spectroscopy. In aqueous solution, the block copolymers associate into particles with hydrodynamic radii (R(H)) ranging in size from R(H) 70 to 130 nm, depending on the block copolymer architecture and the polymer molecular weight. Larger R(H) and critical association concentration values were obtained for copolymers containing poly(S-benzyloxycarbonyl-l-cysteine) compared to their poly(γ-benzyl-L-glutamate) analogue. FTIR investigations revealed that the poly(γ-benzyl-L-glutamate) block adopts a helical conformation, while the poly(S-benzyloxycarbonyl-L-cysteine) block exists as β-sheet.     

Photosynthetic response of tetraploid and hexaploid wheat to water stress

Photosynthetic characteristics of ear and flag leaves of wheat species, tetraploid Triticum dicoccoides Kom and hexaploid Bima1, were studied in plants grown under well-watered (WW) and water-stressed (WS) conditions. Compared to ears, flag leaves exhibited higher photosynthetic rate (P _N) at the filling stage, but more severe decrease under WS. P _N in the tetraploid wheat ear remained higher than that in the hexaploid wheat during the grain-filling stage. Water stress decreased PN in both the organs; this decline was caused by a reduction in Rubisco activity, not by drought-induced stomatal limitation. Tetraploid wheat ears exhibited higher relative water content and water-use efficiency than that of hexaploid wheat, under WS. The change in phosphoenolpyruvate carboxylase activity and carbon isotope composition indicated the absence of C₄ metabolism in the ears of both species under both conditions. The improved performance of the tetraploid wheat ears under WS was associated with better water relations.     

Comparison of characterization and microbial communities in rice straw- and wheat straw-based compost for <Emphasis Type="Italic">Agaricus bisporus</Emphasis> production

Rice straw (RS) is an important raw material for the preparation of Agaricus bisporus compost in China. In this study, the characterization of composting process from RS and wheat straw (WS) was compared for mushroom production. The results showed that the temperature in RS compost increased rapidly compared with WS compost, and the carbon (C)/nitrogen (N) ratio decreased quickly. The microbial changes during the Phase I and Phase II composting process were monitored using denaturing gradient gel electrophoresis (DGGE) and phospholipid fatty acid (PLFA) analysis. Bacteria were the dominant species during the process of composting and the bacterial community structure dramatically changed during heap composting according to the DGGE results. The bacterial community diversity of RS compost was abundant compared with WS compost at stages 4–5, but no distinct difference was observed after the controlled tunnel Phase II process. The total amount of PLFAs of RS compost, as an indicator of microbial biomass, was higher than that of WS. Clustering by DGGE and principal component analysis of the PLFA compositions revealed that there were differences in both the microbial population and community structure between RS- and WS-based composts. Our data indicated that composting of RS resulted in improved degradation and assimilation of breakdown products by A. bisporus, and suggested that the RS compost was effective for sustaining A. bisporus mushroom growth as well as conventional WS compost.     

Improved plant regeneration from wheat anther and barley microspore culture using phenylacetic acid (PAA)

Summary The effect of the auxin phenylacetic acid (PAA) on wheat anther and on barley anther/microspore culture was investigated. With PAA the induction response was not usually significantly different from controls but a significantly higher number of green plants were produced in wheat anther and barley microspore culture. For wheat anther culture 100 mg/L PAA was beneficial. For barley microspore culture the optimum levels were from 1 to 100 mg/L, depending on genotype. In barley anther culture there were no improvements using PAA. In wheat anther culture, 145 green plants/100 anthers were obtained with cultivar VeeryS, while the average response from twelve F₁ hybrids in the breeding program was 332 green plants/100 anthers. At least 1000 green plants were obtained using isolated microspores from 100 anthers in barley cv. Igri. With cv. Bruce, regeneration occurred only when 100 mg/L PAA was used. The influence of PAA appears at the embryogenic phase of the culture system. The possible mechanisms by which PAA may improve regeneration are discussed.     

Effect of long term feeding of ammoniated wheat straw treated with or without HCl on blood biochemical parameters in growing male buffalo (Bubalus bubalis) calves

Twenty-four growing male buffalo calves (one year of age; 88.54 +/- 3.81 kg average body weight) were divided into three comparable groups (I, II and III) on the basis of their body weight (BW) in a completely randomised design to study the effect of long term feeding of ammoniated wheat straw (AWS) and hydrochloric acid treated ammoniated wheat straw (HCl-AWS) on blood biochemical changes. The animals were offered a concentrate mixture (CM) along with wheat straw (WS), ammoniated wheat straw (AWS) (4% urea at a 50% moisture level) and hydrochloric acid treated ammoniated wheat straw (HCI-AWS) (4% urea at a 50% moisture level and HCI added to trap 30% of NH3 evolved) in groups I, II and III, respectively for an average daily gain (ADG) of 500 g. All the diets were made iso-nitrogenous by preparing three types of concentrate mixtures of different CP levels. The blood was collected from the jugular vein randomly from three animals of each group initially after 8 months post feeding and subsequently after two months interval up to 14 months of experimental feeding. Due to urea ammoniation, the CP content of WS increased from 3.66 to 8.51 and was further increased to 11.35 due to the addition of HCl during urea-ammoniation of wheat straw. The cumulative period mean plasma glucose values (mg %), in group II (53.13) were significantly (P < 0.001) higher than those in groups I (48.44) and III (50.60). The cumulative period mean values of serum albumin and globulin (g %) were not significantly different and were comparable among the groups I (3.33 and 3.06), II (3.53 and 2.97) and III (3.49 and 2.94). The cumulative period mean values of serum albumin: globulin ratio and total protein values were not significantly different among the different groups. Serum urea and creatinine values were significantly (P < 0.001) higher in group III (58.66 and 2.24) as compared to groups I and II. The cumulative period mean values of serum alkaline phosphatase (ALP) (KA units) did not differ significantly, but serum glutamate pyruvate transaminase (SGPT) and glutamate oxaloacetate transaminase (SGOT) values (units x mL(-1) were significantly (P < 0.001) higher in groups II and III than in group I. The cumulative period mean values of T3 (ng x mL(-1)) did not differ significantly among the groups, but T4 values were significantly (P < 0.001) higher in group III (22.74) than in groups 1 (21.41) and II (20.89), respectively. Since the mean values of all the blood parameters were within the normal range, it may be concluded that feeding of ammoniated wheat straw treated with and without HCl to growing male buffalo calves for fourteen months has no adverse effect on the blood biochemical parameters.     

Thermosensitive Poloxamer 407/Poly(Acrylic Acid) Hydrogels with Potential Application as Injectable Drug Delivery System

Thermosensitive hydrogels are of great interest for in situ gelling drug delivery. The thermosensitive vehicle with a gelation temperature in a range of 30–36°C would be convenient to be injected as liquid and transform into gel after injection. To prepare novel hydrogels gelling near body temperature, the gelation temperature of poloxamer 407 (PX) were tailored by mixing PX with poly(acrylic acid) (PAA). The gelation behaviors of PX/PAA systems as well as the interaction mechanism were investigated by tube inversion, viscoelastic, shear viscosity, DSC, SEM, and FTIR studies. The gelation temperature of the plain PX solutions at high concentration of 18, 20, and 22% (w/w) gelled at temperature below 28°C, which is out of the suitable temperature range. Mixing PX with PAA to obtain 18 and 20% (w/w) PX with 1% (w/w) PAA increased the gelation temperature to the desired temperature range of 30–36°C. The intermolecular entanglements and hydrogen bonds between PX and PAA may be responsible for the modulation of the gelation features of PX. The mixtures behaved low viscosity liquid at room temperature with shear thinning behavior enabling their injectability and rapidly gelled at body temperature. The gel strength increased, while the pore size decreased with increasing PX concentration. Metronidazole, an antibiotic used for periodontitis, was incorporated into the matrices, and the drug did not hinder their gelling ability. The gels showed the sustained drug release characteristic. The thermosensitive PX/PAA hydrogel could be a promising injectable in situ gelling system for periodontal drug delivery.     

Biodiesel production from rubber seed oil using poly (sodium acrylate) supporting NaOH as a water-resistant catalyst

Poly (sodium acrylate) supporting NaOH (NaOH/NaPAA) was prepared by in situ polymerization of aqueous solution of acrylic acid with an over-neutralization by adding excess of NaOH. NaOH/NaPAA presented a promising selectivity for water absorbency and good water retention with negligible swelling capacity in the organic solvents of methanol, glycerol, rubber seed oil methyl esters, and rubber seed oil. NaOH/NaPAA catalysts showed a basic strength of 15.0 < H_ < 18.4 and their basicity increased with the increase of the NaOH loading amount. NaOH/NaPAA catalysts exhibited almost the same catalytic activity in the transesterification of rubber seed oil with methanol under the optimized reaction conditions compared to conventional homogeneous NaOH catalyst. Furthermore, the functional absorbent/catalyst system presented a good water resistance in the transesterification which retained high catalytic activity when a water concentration in the reaction system was less than 2 wt.%.